Most mobile devices are configured to receive removable Universal Integrated Circuit Cards (UICCs) that enable the mobile devices to access services provided by mobile network operators (MNOs). In particular, each UICC includes at least a microprocessor and a read-only memory (ROM), where the ROM is configured to store an MNO profile that the mobile device can utilize to register and interact with an MNO. Typically, a UICC takes the form of a small removable card (commonly referred to as a SIM card) that is configured to be inserted (e.g., using a tray) into a UICC-receiving bay included in a mobile device. In more recent implementations, however, UICCs are being embedded directly into system boards of mobile devices. Notably, these embedded UICCs (eUICCs) can provide several advantages over traditional, removable UICCs. For example, some eUICCs include a rewritable memory that can facilitate eSIM updates for accessing extended features provided by MNOs. eUICCs can also eliminate the need for UICC-receiving bays within mobile devices. The implementation of eUICCs, therefore, not only increases the flexibility of mobile devices, but also simplifies their design and frees up space for other components.
The flexibility provided by eUICCs has recently led to efforts to activate two or more eSIMs on a mobile device so that a user can communicate with two or more respective MNOs. Multiple active eSIMs present a problem, however, as SIM toolkit commands (e.g., TERMINAL PROFILE, ENVELOPE, FETCH, TERMINAL RESPONSE, etc.) are configured to be transmitted over a basic channel using a protocol that does not include information for identifying a source or destination associated with each SIM toolkit command. Specifically, the protocol omits this information because conventional techniques involve only a single physical UICC included in a mobile device, and, therefore, the source or destination associated with each SIM toolkit command is inherent. Consequently, when multiple eSIMs are active within an eUICC of a mobile device, there is a need to identify the source eSIM from which a SIM toolkit command issues or the destination eSIM to which a SIM toolkit command is directed.